1. Field of the Invention
The present invention relates to a liquid crystal display, and more particularly to a technique effectively applied to a back light using a point light source such as a white color light emitting diode (LED: Light Emitting Diode).
2. Description of the Related Arts
Conventionally, in a liquid crystal display module, a back light (light source) is disposed in the rear (on the back face) of a liquid crystal display panel, whereby an image is displayed by applying a light from the light source to the liquid crystal display panel.
In the liquid crystal display module for use in a portable telephone or the like, a point light source such as a white light emitting diode (LED: Light Emitting Diode) is recently used as the light source for the back light to save weight (Patent document 1 (Japanese Patent Laid-open No. 2005-38749)).
FIGS. 13 and 14 are schematic views for explaining the back light using the conventional white light emitting diode, wherein FIG. 13A is a schematic plan view and FIG. 13B is a side view.
FIG. 13 illustrates the back light having one white light emitting diode, and FIG. 14 illustrates the back light having two white light emitting diodes 11. The back lights of FIGS. 13 and 14 are disclosed in the patent document 1.
Each back light as shown in FIGS. 13 and 14 has the white light emitting diode 11 disposed on the side face of a light guide plate 2 and an outgoing light control board 5 disposed on the surface of the light guide plate 2 on the side of the liquid crystal display panel.
The outgoing light control board 5 has a plurality of convex portions 501, in which each convex portion 501 is at least partly circular in cross-sectional shape.
Also, the present applicant has already made an application for a back light using a white light emitting diode as the light source and a light guide member to reduce the thickness and weight of the back light (patent document 2 (Japanese Patent Application No. 2005-352167)).
FIG. 15 is a schematic view for explaining another back light using the conventional white light emitting diode, wherein FIG. 15A is a schematic plan view and FIG. 15B is a side view. The back light of FIG. 15 is disclosed in the patent document 1.
The back light of FIG. 15 has a light guide member 3, an incident light adjustment member 1 disposed on the light guide member 3, and a white light emitting diode 11 disposed on the incident light adjustment member 1.
The incident light adjustment member 1 has a plurality of convex portions 101, in which each convex portion 101 is at least partly circular in cross-sectional shape. In FIG. 15, reference sign 11R denotes a rear face reflecting sheet. Also, in FIGS. 13 to 15, reference sign AR denotes an effective light emitting area.